Snap fasteners are used on garments to a large extent. A snap fastener has a structure in which a female snap member that is also referred to as socket member and a male snap member that is also referred to as stud (which are collectively referred to as snap members) are resiliently engaged with and disengaged from each other. The snap members are attached to the oppositely disposed sides of respective pieces of fabric so as to face each other.
For examples, as shown in FIG. 12, a female snap member 1 and a male snap member 2 are attached to the oppositely disposed sides of pieces of fabrics 5, 6 by means of respective attaching members 3, 4 that are referred to as prong members from the other sides of the pieces of fabric.
If a snap member that is attached to the fabric of garments is easily detached, an infant can swallow the snap member and/or the attaching member. Therefore, it must be guaranteed that the force for detaching a snap member exceeds a predetermined level. Thus, in sewing factories, the force required for detaching a snap member is tested so as to keep the snap members produced from the factory are under control and make sure that force exceeding a predetermined level is required for detaching each of them.
For this reason, sewing companies in many countries adopt the European Standard “BS EN71-1: Safety of Toy, Mechanical and Physical Properties”, which defines that the force that can detach a snap member needs to be equal to or greater than “90N 10 seconds”.
Known gauges for measuring the force required for detaching a snap member typically have a structure as shown in FIGS. 9 through 11.
The gauge comprises a base 10, a stage 11 arranged on the top surface of the base 10 and adapted to receive thereon a snap member attached to a piece of fabric and placed on it, a means for pressing the fabric 21 adapted to press the fabric around the snap placed on the stage 11, a constraining means 31 for constraining the sides of the snap member, a pulling means 41 for pulling the constraining means 31 constraining the snap member away (substantially vertically upward) from the means for pressing the fabric 21 and a gauging means 51 for gauging the pulling force of the pulling means 41.
The stage 11 includes a support table 12 rigidly secured to the top surface of the base 10, a support block 14 rigidly secured to the support table 12 by way of a support bolt 13 and a die 16 supported by the support block 14 by way of a resilient spring section 15 formed by laying a plurality of leaf springs, every other of which is laid upside down. A snap member attached to a piece of fabric is placed on the top surface of the die 16.
The means for pressing the fabric 21 includes a support member 22 standing upright from the support block 14, a fabric presser arm 24 supported at a middle section thereof by the support member 22 at the top end of the latter by way of a support shaft 23 so as to be able to swing around the shaft and press the fabric at an annular front end part thereof, a screw shaft 25 horizontally screwed into a middle section of the support member 22, a fabric presser arm regulating dial 26 engaged with the screw shaft 25, a link holder 28 rotatably supported by the fabric presser arm regulating dial 26 by way of a bearing 27 and a link 29 linking the link holder 28 and the rear end of the fabric presser arm 24.
The constraining means 31 includes a threaded bolt 32 linked to a chain 52 extending downward from the gauging means 51 by way of a joint 53, a jaw support plate 33 arranged at the lower end of the threaded bolt 32, three jaws 34 arranged to surround the snap member and having at the front ends thereof respective engaging portions 34A adapted to be engaged with the sides of the snap member, support shafts 35 rotatably holding middle portions of the jaws 34 to the jaw support plate 33 so as to allow the front end engaging portions 34A of the jaws 34 to spread and become closed, turning/biasing means 36 for turning/biasing the respective jaws 34 around the corresponding respective support shafts 35 so as to operate as fulcrums and open the front end engaging portions 34A of the jaws 34 and a cam section 37 arranged so as to abut the base end portions of the jaws 34 and turn the jaws 34 around the respective support shafts 35 in order to close the front end engaging portions 34A of the jaws 34 when it is engaged with the threaded bolts 32 and driven to move downward. The turning/biasing means 36 comprise respective coil springs arranged respectively at the outsides of the corresponding jaws 34. A jaw regulating dial 37A is arranged on the cam portion 37 as an integral part of the latter.
The pulling means 41 includes an upright frame 42 standing on the top surface of the base 10, a support frame 43 rigidly secured to an upper part of the upright frame 42, a gauge support plate 45 vertically and slidably fitted to the support frame 43 by way of a sliding member 44 and having the gauging means 51 fitted to the front side thereof and a pulling up mechanism 46 for pulling up the gauge support plate 45. The pulling up mechanism 46 comprises a top plate 47 arranged rectangularly to the top end of the gauge support plate 45, a threaded bolt 48 screwed vertically into the support frame 43 to hold the top plate 47 and a wheel 49 rigidly secured to the top end of the threaded bolt 48.
The gauging means 51 comprises a commercially available tensile force measuring gauge 51A.
The necessary force for detaching a snap member is measured by means of the above described configuration in a manner as described below.
When the snap member attached to a piece of fabric is placed on the top surface of the die 16, the jaw regulating dial 37A is rotated so as to pinch and constrain the snap member at the sides thereof by means of the three jaws 34.
At the same time, the fabric presser arm regulating dial 26 is rotated so as to press the fabric by means of the annular front end part of the fabric presser arm 24. Then, the wheel 49 is rotated to pull up the snap member that is constrained by the jaws 34 slowly by means of the tensile force measuring gauge 51A and obtain the reading of the tensile force measuring gauge 51A. If the snap member is not detached from the fabric beyond a predetermined level of pulling force, it is guaranteed that the snap member withstands a predetermined level of force trying to detach it from the fabric. When the snap member is pulled until it is detached from the fabric, the necessary force for detaching it from the fabric is observed.
Generally, when measuring the force required for detaching a snap member, it is necessary to constrain the snap member by force not less than 200N because the force required for detaching a snap member is normally about 200N.
With conventional measuring instrument for detaching force of snap members, the operator operates the jaw regulating dial 37A by rotating it to constrain or release the snap member. Such a practice is accompanied by the following problems.
(1) When measuring the snap member detaching force, the jaw regulating dial 37A can be tightened excessively in fear of accidental release of the snap member from the jaws 34. Then, a large force is required to loosen the jaw regulating dial 37A that has been tightened excessively after measuring the snap member detaching force. However, since the operator manually rotates the jaw regulating dial 37A, the force applied to it cannot be very large. For this reason, the operation of measuring the snap member detaching force is a burden to the operator.
(2) As the snap member is constrained by excessive force, the front ends of the jaws 34 can be driven between the snap member and the fabric to separate the snap member from the fabric and the snap member can be deformed. There can be occasions where the snap member detaching force is not correctly measured due to such phenomena.
Additionally, with conventional measuring instrument for detaching force of snap members, the operator operates the fabric presser arm regulating dial 26 by rotating it to press or release the fabric. Such a practice is accompanied by the following problems.
(3) When measuring the snap member detaching force, the fabric presser arm regulating dial 26 can be tightened excessively in fear of accidental detachment of the fabric from the fabric presser arm 24. Then, a large force is required to loosen the fabric presser arm regulating dial 26 that has been tightened excessively after measuring the snap member detaching force. However, since the length of the fabric presser arm 24 from the fulcrum to the link side end is shorter than the length thereof from the fulcrum to the die side end, a large force is required for the operator to operate the fabric presser arm regulating dial 26 to rotate it.
(4) The fabric presser arm 24 is made longer between the fulcrum and the die side end thereof than between the fulcrum and the end thereof located close to the fabric presser arm regulating dial 26 so that the fabric presser arm 24 can be rotated by a necessary angle by rotating the fabric presser arm regulating dial 26 only to a small extent in view of the fact that it is necessary to secure a gap of about 10 mm between the fabric presser arm 24 and the die 16 when the snap member that is attached to the fabric is placed on the die 16. Therefore, the operator is required to exert a large force when rotating the fabric presser arm regulating dial 26. For this reason, the operation of measuring the snap member detaching force is a burden to the operator.
Thus, the first object of the present invention is to provide a constraining device that can reliably constrain a member of constraint without putting a burden on the operator.
The second object of the present invention is to provide a measuring instrument for detaching force of snap member that can lessen the load of the operator and accurately measure the necessary force for detaching a snap member.